1. Field of the Invention
This invention relates to an adaptive filter device for removing noise from a picture signal. This invention also relates to a method of adaptively filtering a picture signal.
2. Description of the Related Art
In a prior-art adaptive filter device for removing noise from a picture signal, a decision is made as to whether every 1-pixel-corresponding portion of an image represented by the picture signal is still or moving. Then, each segment of the picture signal which relates to a still 1-pixel-corresponding image portion is subjected to a filtering process in a temporal direction (a time-base direction). On the other hand, each segment of the picture signal which relates to a moving 1-pixel-corresponding image portion is not subjected to the filtering process. Thus, it tends to be difficult to remove temporal-direction noise from segments of the picture signal which represent moving image portions.
The temporal-direction noise decreases the quality of the image represented by the picture signal. In the case where the prior-art adaptive filter device is followed by a data compressing stage, the temporal-direction noise consumes bits of the compression-resultant picture signal. When the bit rate of the compression-resultant picture is limited to a low level, the temporal-direction noise considerably decreases the quality of images represented by the compression-resultant picture signal.